I have fiberglass bumpers ready to go on. Question. What would be the best method to secure the bolts to bumper mounting tabs so the bolt ot nut (depending) wont spin when i tighten or loosen to remove? Mounting tabs are fiberglass also.

Michael

I would weld the nuts or bolts to a steel plate glued to the back of the bumper tab. That way one will hold the plate in position as you start to loosen the other. Not sure that is the best explanation but hope it helps.

I think you will need to place the bumper in position, mark the tabs for holes, drill, and then place the mounting plates. You may have already drilled the bumper tabs since you say you are ready to go.

Jim

Thanks Jim

No welding here. But i see what you are saying. No holes drilled yet. Still thinking. JB weld? Liquid nails? Only plan on talking off for paint but will need them on for fitment and such. But afraid of to much torque will bust that loose i am sure. But your solution seems the only way. I can take a bracket to a welder for the bolts then re bolt the bracket to the mounting tab.

Yes?

Michael

Hi Michael,

Let me weld you up some "nutted" backing plates... I still owe you for the fine hospitality a few weeks ago!

What size & thread count bolts are you using? If you want, drive over to my house in Davis some evening this week with the bumpers and we'll whip some up.

PM me for contact info and days/times that work for you.

Geoff

PM sent

Michael,
You can use JB Weld to put on the front bumpers but you should make sure you have road hazard coverage on your tires because that front bumper can be sharp when you run over it! I saw one take out two tires on a car at the track...

Wow Rob I had no idea! Thanks!

I am talking about keeping the bolt or nut tight while I thighten or loosen.

ps Stay out of the drugs in those a ambulances you ride in.

Good advice! But lately, I am in one of three offices. If I am in an ambulance, somebody is in trouble

i have mine mounted by welding two nuts to the body and having a flat glass with big bolts and washers to hold it , and holes right through the exterior for quick removals
but you could just bolt a metal mount bracket to the body with a couple of bolts, one or two bolts to mount the glass to the bracket, just make sure the bracket on the glass side is beefy maybe layering a quarter inch hardwood between the glass would give it extra support,
i wish i had pictures of this

Hi Michael -

Our phone discussion today got me thinking...

It'd be easy to weld two nuts onto a 1/8" thick by 2" wide plate (four sets for the front and rear bumpers). However, you don't necessarily need to bolt the nutted backer plates to the fiberglass bumper mounting tabs using small bolts, or even fiberglass the backer plates to the mounting tabs, to keep the two sets together while you mount each bumper.

In fact, you might wants some wiggle room -- we could drill slightly larger than needed holes in the FG mounting tabs, use tape to temporarily hold the dogbone / mounting tab / backing plate sandwich together. You could even add a fender washer between the dogbone and mounting tab to spread out the load on the fiberglass mounting tab. That way you'll have some fine adjustment up-down/left-right. The tape would merely hold it together while you feed the bolts through the body into each dogbone / (fender washer) / mounting tab / backing plate.

Anyone?

Geoff

Ok but what is going to keep the nutted backers from spining when tightning up?

I think he is saying both holes with nuts thru one rectangular backer piece so the bolts will keep the backer from spinning. Think dogbone but metal backer plate.

Jim

Yupper. Thanks for making what I said clear. Wanna move in so my wife won't continue to be angry at me for saying things the wrong way???

I mounted my rear FG bumper on my race car using regular bolts to the FG tabs. I taped it up first to get the fit right.

Wow I am dumb! Cant spin with two bolts now can they! It sucks getting old.

Will get in touch Geoff when i get the back plates.

Michael

To keep the bumper on the brackets, make darned sure you clean the gluing area REALLY well.

We're talking surgical clean with multiple cleanings and wear gloves. Fingerprints have delaminated many an aerospace part.....I'm sure there is wax (a compound in the resin) and/or mold release somewhere on that bumper, and fingerprints on the bracket. One or more of these can cause the glue joint to fail....

For aerospace, where you don't want parts falling off, we would abrade the gluing surfaces first. Next we used Fantastic cleaner (low residue) for several cleanings with fresh paper towels each time. Next, several cleanings of lacquer thinner with fresh paper towels each time, and lastly use pure grain alcohol (aka missle cleaner) or a higher octane rubbing alcohol found in the store.

One last suggestion (belt AND suspenders) reclean and glass over the bracket (after the JB sets) to spread the vibrational load path. In other words, spread the load out over a larger surface area to make a better glue joint to decrease the likelyhood of delamination.

Yeah, I know it's anal in an aerospace way, but probably cheaper and less traumatizing than running over your own bumper.

The brackets are already mounted on the bumper by the manufacturer... but your cleaning description is a good one!

Geoff

Nope, won't work. My translation skills only work with other males who have 914's.

Jim